TLS certificate vetting process
The following steps depend on the vetting level you chose. Certificates have 3 vetting levels - DV is simply confirmed by e-mail, but OV and EV vetvetting is done by actively verifying the company details and contacts for the order. It takes some time.
Once the verification process is complete, the certificate is issued and can be installed on your webserver.
Other types of certificates have different validation, see the appropriate article for more information.
FQDN domains included in the certificate order must be vetted in any case. This is done by email and every time the CA sends a vetting email to the admin, administrator, hostmaster, postmaster and webmaster addresses on the vetted domain.
If you are not able to accept emails on the domain, you can use alternative vetting instead. This is done with a DNS record or file uploaded via FTP to the domain you are ordering the TLS certificate for.